A 35-year-old male with a rare genetic disorder presents with delayed wound healing, immune dysfunction, and growth retardation. Laboratory tests reveal low zinc (Zn²⁺) levels. His physician explains that zinc plays a crucial role in stabilizing transcription factors involved in gene expression and immune function. Which of the following protein structures is primarily stabilized by Zn²⁺ and plays a role in DNA/RNA binding and gene regulation?
